“Abnormalities” on structural images Findings and clinical implications

1. “Abnormalities” on structural imagesFindings and clinical implications Robert D. Zimmerman MD FACR Weill Cornell Medical College

2. Definition Incidental finding (IF) “ A finding that has potential health or reproductive importance discovered in the course of conducting research but is beyond the aims of the study” • Wolf et al. Managing incidental findings in human subjects research: analysis and recommendations. J Law Med Ethics 2008: 36 219

3. Ifs encountered depend on • Age of subject population • Affects types of findings & their prevalence • Imaging protocols used • Study exam is not a clinical exam and therefore may not detect an abnormality even if present • If only perform anatomic T1 weighted sequence will fail to detect processes that primarily alter tissue content rather than tissue volume • Subclinical or asymptomatic processes • Stable or slowly progressive processes • How we (I) define IF • Some findings are normal variants or so unlikely to be clinically significant that are not worth mentioning

5. Population • 422 studies reviewed since 2008 • Subjects 5-20 years old • ~ Mean approximately 15 • No clinical neurologic abnormalities

6. IFs20 subjects – 4.8% • Aqueductal stenosis with “arrested” hydrocephalus - 1 • Middle fossa arachnoid cyst – 6 • Focal or diffuse enlargement of subarachnoid spaces and or low brain volume – 3 • Chiari I malformation – 4 • Focal white matter abnormality - 1 • Cavum septum pellucidum – 3 • Intraventricular cyst – 1 • Suspected aneurysm - 1

7. Review of literature • IF in 10-50% of subjects • Pediatric subjects (2 studies) ~ 425 combined • Incidence - 21% • However > 50% had sinusitis • Included pineal cysts and prominent perivascular spaces (normal variants) • Clinical f/u in 1/3 • Similar findings as in our population • Adult and pediatric subjects • 18% IF • 2/3 sinus disease • Aneurysm, 3 brain tumors

8. IF classification • 1) Clinically significant • Likely to need treatment • Surgery, medical management • 2) Potentially clinically significant • Probably will not require clinical treatment but may need: • Full diagnostic MR or other imaging test • Referral to a neurologist or neurosurgeon • Follow-up assessment to insure not a progressive process • 3) Incidental finding not likely to require intervention • Does patient need to know? • Should there be follow-up imaging

9. Practical and ethical implications • No consensus in US or Europe • Are researchers obligated to look for and report IF? • Researchers ~75% • Subjects - > 95% • What images should be reviewed by a neuroradiologist? • Reactive – Only ask for review when researcher sees something troublesome • Proactive – Neuroradiologist reviews all images • Very proactive – Include diagnostic sequences (e.g. FLAIR) even not required for study design

10. IFType 1 • Aqueductal stenosis with hydrocephalus – 1 • Asymptomatic however likely to become symptomatic over time • Surgery • Third ventriculostomy

13. IF Type 3 • Middle fossa arachnoid cyst – 6 • Cavum septum pellucidum – 3 • Intraventricular cyst – 1 • Asymptomatic • Lesions usually static • No intervention necessary • Probably should inform family of presence of arachnoid cyst. • Arachnoid cysts may rarely enlarge and become hemorrhagic with head trauma

15. Arachnoid cysts • Congenital lesions due to splitting of the inner and outer layers of arachnoid • Cells lining cyst secrete CSF • Locations • Middle cranial fossa • Cerebral convexity • Suprasellar cistern • Posterior fossa • Small and medium size cysts asymptomatic • Large cysts may become symptomatic • Treatment – Cyst fenestration

18. IFType 2 • Focal or diffuse enlargement of subarachnoid spaces and/or low brain volume -3 • Chiari I malformation – 4 • Focal white matter lesion -1 • If static and asymptomatic no intervention needed • If progressive needs to be followed and/or treated

20. White matter lesions“UBO’s” Ischemia TraumaDemyelination???Usually asymptomaticNon-progressive

21. Chiari malformation • Disclaimer – I hate Chiari Malformation • Rant #1 • History • 1891: Chiari (German not Italian) reported 4 types • 1894: Arnold describes a single individual with meningomyelocoele and mentioned in passing that the hindbrain is abnormal • 1912 – Students of Arnold review the hindbrain anomalies in what is now called Chiari II malformation and name them the “Arnold Chiari malformation” • Now – Term “Arnold Chiari” often used to describe all of these malformations (Wikipedia) • So Arnold gets credit because of 1 incompletely described case of Chiari II and for all of the other malformations that he did not describe

22. Chiari malformation • Rant 2 • At least 2 separate anomalies and maybe as many as 4 • Chiari I completely separate from II-IV • Chiari II – Spina bifida • Suite of brain & spinal cord abnormalities discovered at birth and now often in utero • Primary defect is failure to form cerebral ventricles at appropriate time leading to small posterior fossa • Genetic and/or nutritional • Folic Acid deficiency • Surgery to correct meningomyelocoele (in utero) • Shunt for hydrocephalus • Chiari III and IV very rare • May be severe versions of Chiari II or separate diseases • I have never seen a Chiari IV

23. Chiari I malformation • Not a brain anomaly • Not one thing • Anomalies of the osseous cranio-vertebral junction and/or posterior fossa • Cerebellar tonsils “trapped” in the upper cervical spinal canal leading to compression of the brain stem and altered CSF flow • Secondary syringomyelia and/or hydrocephalus • Any disorder that traps tonsils below foramen magnum will present with similar clinical manifestations

24. Clinical manifestations • Tussive and/or positional headache • Signs of brain stem dysfunction • Vertigo • Nystagmus (abnormal eye movements) • Lower cranial nerve dysfunction • Syringomyelia • Loss of sensation of pain and temperature • Vibration and position • Eventual weakness and muscle atrophy • Insidious onset • Hydrocephalus • Treatment • Surgical decompression of the skull base • Shunt syrinx cavity and hydrocephalus • Surgery halts progression but does not restore lost function

25. Imaging features • Osseous abnormalities • Platybasia • Short clivus • Small volume posterior fossa • Assimilation of C1 into skull base • Brain/CSF • Narrow craniovertebral junction CSF space • Tonsil and brain stem distorted and impacted into cervical spinal canal • Syringomyelia (cord cyst) • Hydrocephalus • Tonsil more than 5 mm below foramen magnum • Symptomatic Chiari usually > 10 mm

26. Rant #3 • It is hard to reliably measure tonsilar position • Tonsils often off midline and asymmetric • Precise definition of inferior margin of foramen magnum difficult to determine • Therefore very difficult to differentiate between normal low lying tonsils (< 5 mm) and mild Chiari I when no other abnormalities • Don’t want to miss an asymptomatic Chiari I since may slowly progress to irreversible neurologic dysfunction

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35. Neoplasms • Brain neoplasms second most common tumors in children (after leukemia) • Many highly malignant acutely symptomatic • Lower grade tumors • Juvenile Pilocytic Astrocytoma • Low grade (but malignant) astrocytoma • Oligodendroglioma • Pituitary adenomas

38. Incidental vascular abnormalities • Aneurysm • Out pouching of cerebral artery usually near base of brain • Rupture leads to catastrophic intracranial hemorrhage • However • Small unruptured aneurysms (< 5 mm) typically don’t bleed • Aneurysms rare in children and young adults • Acquired not congenital lesions • If suspect aneurysm on research study MRA can confirm or exclude diagnosis and provide treatment guidance

40. Arteriovenous malformation (AVM) • Congenital abnormal connection between arteries and veins without intervening capillary bed • Creates high flow “short circuit” • Typically presents in young adults with intracerebral hemorrhage or seizures • Discovered incidentally in many individuals undergoing MR for other reasons (e.g headache) • Treatment • Surgery with or without endovascular partial ablation if presents with hemorrhage • May treat or follow with imaging if no hemorrhage